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  1. Qt for Python
  2. PYSIDE-803

QThread Freezes GUI

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Details

    • Bug
    • Resolution: Fixed
    • P1: Critical
    • 5.14.2
    • 5.11.1
    • PySide
    • None
    • Python 3.6, PySide2 5.11.1, PyQt5 5.11.2. This problem would occur in both Linux (Kubuntu 18.04.1) and Windows 10 (so far as I have tested).
    • All
    • 14299e5f5 (dev), 619a44493 (6.5)

    Description

      It is not completely freezing. However, when I do some heavy tasks in QThread, the GUI responds slowly. For instance,

       

      import sys
from PySide2.QtCore import QThread
from PySide2.QtWidgets import (QApplication, QWidget, QPushButton, QComboBox, QVBoxLayout)

class Task(QThread):
    def run(self):
        # some heavy tasks
        print('task started')
        k = 0
        for i in range(10000):
            for j in range(50000):
                k += 1
        print('task finished')

class Gui(QWidget):
    def __init__(self):
        super().__init__()
        layout = QVBoxLayout()
        button = QPushButton('click me')
        button.clicked.connect(self.do_task)
        combobox = QComboBox()
        combobox.addItems(['1', '2', '3', '4', '5'])
        layout.addWidget(button)
        layout.addWidget(combobox)
        self.setLayout(layout)

    def do_task(self):
        self.thread = Task()
        self.thread.start()

if __name__ == '__main__':
    app = QApplication(sys.argv)
    window = Gui()
    window.show()
    sys.exit(app.exec_())

      Here is the example GIF animation.


      However, if I use PyQt5 to run the script (replacing PySide2 module), the GUI response will not delay at all.

      Attachments

        Issue Links

          is required for

          Suggestion - Public suggestions PYSIDE-1203 Documentation/Examples For How To Develop Multithreaded Applications

          • P3: Somewhat important - Should be fixed, but doesn't affect the release in any way.
          • Reported
          relates to

          User Story - Created by Jira Software - do not edit or delete. Issue type for a user story. PYSIDE-1108 Improve handling of threading issues between Python and Qt world

          • P1: Critical - Urgent and Important, will STOP the release if matched with set FixVersion field. This includes regressions from the last version that are not edge cases; Data loss; Build issues; Flaky tests; All but the most unlikely crashes/lockups/hanging; Serious usability issues and embarrassing bugs & Bugs critical to a deliverable. This is the highest possible priority for requirements.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. PYSIDE-1657 Possible deadlock on signal connect/emit

          • Not Evaluated - Not yet evaluated/prioritized
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. PYSIDE-1919 Segfault when garbage collector grabs object with connected signal

          • P2: Important - Urgent, should be fixed, but will not stop the release.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. PYSIDE-2034 QMessageBox.information in main thread blocks worker thread.

          • P3: Somewhat important - Should be fixed, but doesn't affect the release in any way.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. PYSIDE-2302 QThreadPool locking main thread when creating QImage in PySide2 and PySide6

          • P3: Somewhat important - Should be fixed, but doesn't affect the release in any way.
          • Closed

          Suggestion - Public suggestions PYSIDE-1788 overriden methods should allow threads during long Qt operations

          • Not Evaluated - Not yet evaluated/prioritized
          • Closed
          resulted in

          Bug - A problem which impairs or prevents the functions of the product. PYSIDE-1681 GIL deadlock in qInstallMessageHandler

          • P2: Important - Urgent, should be fixed, but will not stop the release.
          • Closed
          mentioned in

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              ctismer Christian Tismer
              alan13wake Sean Wu
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              Dates

                Created:
                Updated:
                Resolved:

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